Coating apparatus

ABSTRACT

This invention relates to coating apparatus of the type in which an article to be coated is immersed in a main fluidized bed of the coating material. At least one supplementary fluidized bed is provided which contains a supply of additional coating material, the level of the supplementary bed being capable of being raised to a level above that of the main bed whereby additional coating material is transferred from the supplementary bed to the main bed to replenish the coating material therein. Once the desired level has been achieved, the level of the supplementary bed is lowered and any surplus coating material is arranged to fall back into the supplementary bed.

United States Patent [191 Grenfell l COATING APPARATUS [75] Inventor: Julian Pascoe Grenfell, Pyrford,

England [73] Assignee: Badalex Limited, Weybridge,

England [22] Filed: Oct. 4, 1972 [21] Appl. No.: 294,995

[30] Foreign Application Priority Data Oct. 5, 1971 Great Britain 46235/71 May 19, 1972 Great Britain 23618/72 [56] References Cited UNITED STATES PATENTS 485,906 11/1892 Brown 228/37 X 2,506,317 5/1950 Rex 117/100 B X 2,574,493 1 1/1951 McLean 209/474 Aug. 6, 1974 Primary Examiner-Morris Kaplan Attorney, Agent, or Firm-Lawrence E. Laubscher 5 1 ABSTRACT This invention relates to coating apparatus of the type in which an article to be coated is immersed in a main fluidized bed of the coating material. At least one supplementary fluidized bed is provided which contains a supply of additional coating material, the level of the supplementary bed being capable of being raised to a level above that of the main bed whereby additional coating material is transferred from the supplementary bed to the main bed to replenish the coating material therein. Once the desired level has-been achieved, the level of the supplementary bed is lowered and any surplus coating material is arranged to fall back into the supplementary bed.

5 Claims, 5 Drawing Figures PAIENTED RUB 5 SHEEI 1 BF 3 N Q X m A w a\ 1/ a mm Q J a Q m, r A J mm 9 k a. 2. ix 2.. a r L r L a in. W M m f -i u iv lllllllllllllllllllllll II llllllllllllllllllllllllll IL W PAIENTED 81974 3,827,400

SHEET 2 or 3 AIR SUPPLY 15 AIR SUPPLY 33 FIG. .3

COATING APPARATUS This invention relates to coating apparatus of the type in which an article to be coated is immersed in a fluidized bed of the coating material in powder form.

In the coating of articles by means of a fluidized bed of powdered coating material, one method involves the establishment of the fluidized bed, into which the articles to be coated, usually preheated, are immersed. A coating of the powder adheres to each article, and the powder coat can be made into a coherent coating, sometimes by the heat of the preheated article or sometimes by subsequent heat treatment, or both. The coat ing process can be repeated if necessary to secure an adequately thick coating.

In some circumstances, it is required that the article should be immersed in the fluidised bed to a specific depth. For example, in the coating of certain electrical components, such as capacitors, it may be required to coat components, such as capacitors, it may be required to coat the body of a component, including the junction between the component and its lead-out wires, leaving the wires themselves uncoated.

This operational requirement necessitates that the level of the bed of fluidized material should be maintained to fairly close limits, and this is sometimes a matter of difficulty. In the coating of substantial numbers of articles, the material of the bed is consumed, and must be replenished from time to time. In addition, the level of the fluidized material depends to some extent upon the supply of air used for fluidized it, and any incidental variations may give rise to variations of fluidized bed level.

The present invention provides coating apparatus comprising a first recepticle, means for producing coating material in a fluidized condition in the receptacle, a second receptacle, means for producing coating material in a fluidized condition in the second recepticle, and means for inducing flow of material in a fluidised condition from the second receptacle to the first receptacle.

Features and advantages of the invention will appear from the following description of embodiments thereof, given by way of example, in conjunction with the accompanying drawings, in which:

FIG. 1 is a fragmentary side elevational view of a fluidized bed apparatus; Y

FIG. 2 is a plan view of the apparatus of FIG. 1;

FIG. 3 is a sectional view taken on the line l1l-111 of FIG. 1;

FIG. 4 is a view similar to that of FIG. 3 showing a further fluidized bed apparatus; and

FIG. 5 is a view similar to that of FIG. 4 showing yet another fluidized bed apparatus.

Referring to the drawings, the apparatus comprises an elongated base, comprising longitudinal side walls 10, end walls 11 and a base plate 12. Running along the length of the base are two partitions 13 and 14; these partitions run the full length of the base, and so define a central cavity 15 and side cavities 16 and 17. The top of the base portion is closed by an air permeable diaphragm 18, the diaphragm closing the three cavities 15, 16 and 17. Secured to the base portion above the diaphragm is an upper container 19, secured by bolts such as which also serve to hold the parts of the base together. Within the container 19 are two longitudinal dividers 21 and 22 which are parallel to each other and to the sides of the container, the dividers being arranged above the partitions 13 and 14 respectively, and secured to them by bolts as at 23. As is shown more clearly in FIG. 3, the upper edges of the dividers are tapered to a fine edge. End members 24 are provided for the dividers.

In this way, there are provided within the container 19 a central region 26, disposed above the cavity 15, and chambers 27 and 28 disposed above the cavities 16 and 17. The bottom plate of the base portion is carried on vibration mountings 29 and 30 from a series of support columns 31 and 32, from a base platform 33, and a vibrator assembly 34 is disposed between the base platform and the lower part of the base portion, so that the upper part of the general assembly can be vibrated 1n use.

Means 15 are provided for supplying air under pressure to the cavity 15, and a separately controllable supply 16 of air to the cavities 16 and 17.

In use, powder coating material, which is to be applied to an article, such as 35 to be coated is placed within the chamber 26. The volume of powder inserted is such that with a suitable supply of air to the plenum chamber formed by cavity 15, a fluidized bed will be established in the chamber 26. The article 35, conveniently pre-heated, can be inserted into the chamber or, as may be more convenient, the entire assembly can be lifted up to an extent such that the article becomes immersed in the fluidized material in the chamber 26. After a suitable time, the article is withdrawn from the fluidized bed, for subsequent treatment.

In this coating operation, the fluidized material in chamber 26 is arranged substantially to fill that chamber but at the end of the dipping operation, or a series of such operations, it may be that the material then contained in the chamber is insufficient to raise the level of the fluidized bed to the upper extremity of the chamber, defined by the sharp edges of the dividers 21 and 22.

Accordingly, further fluidized material is inserted into the chambers 27 and 28 and this material can be fluidized by the supply of air to the plenum chambers provided by cavities 16 and 17. It is arranged that during the dipping operation the quantity of material and degree of fluidising is such that the level of material in these chambers is below the top edge of the inner chamber. At the end of a dipping operation or of a series of such operations the air pressure in chambers 16 and 17 is increased to raise the level of the supplementary beds in chambers 27, 28 to an extent sufficient to cause the fluidized material in the two outer chambers to spill over into the central chamber, after which the pressure in the cavities l6 and 17 is reduced, so that the level of material in the two outer chambers 27 and 28 will fall. If an excess of material has by this means been fed into the central chamber, which remains fluidized, the excess material will spill back into the two outer chambers, leaving the central chamber precisely filled at the air pressure then existing in cavity 15. The dipping operation can then be repeated as desired.

As the fluidized material is used up, it may be necessary to replenish the material in the outer chambers 27 and 28 from time to time, but such replenishment will be required relatively infrequently.

Referring now to FIG. 4, the apparatus comprises a base 40, longitudinal side walls 41, end walls 42 and a base plate 43. Running along the length of the base is a partition 44 which defines cavities 45 and 46. The top of the base portion is closed by an air permeable diaphragm 47, the diaphragm closing the cavities 45 and 46. Secured to the base portion above the diaphragm is an upper container 50, secured such as by bolts which also serve to hold the parts of the base together. Within the container 50 is a longitudinal divider 51 which is parallel to the sides of the container, the divider being arranged above and secured to the partition 44 such as by bolts. The upper edge of the divider 51 is tapered to a fine edge.

In this way, there are provided, within the container 50 a main chamber 52, disposed above the cavity 45, and a supplementary chamber 53 disposed above the cavity 46. The bottom plate of the base portion can be carried on vibration mounting such as from a series of support columns mounted on a base platform, and a vibrator assembly disposed so that the upper part of the general assembly can be vibrated in use in the manner already disclosed.

Means 45' are provided for supplying air under pressure to the cavity 45, and a separately controllable supply 46' of air to the cavity 46.

Adjacent the container 50 is a bellcrank lever 55 having arms 56 and 57 mounted on stub shaft 58. The free end of arm 56 is connected by rod 59 to an air cylinder 60 whereby the lever can be pivoted on shaft 58. Arm 57 extends over charging chamber 53 such that a paddle 61 depending from its free end extends into the charging chamber. Thus, with cylical actuation of air cylinder 60, the paddle can be moved vertically and horizontally, with its free end oscillating along the line of arrow A-A.

In use, the coating of an article is carried out in the manner already described using the fluidised bed produced in main chamber 52.

When further fluidized material is required due to a drop in the level of the fluidized bed in chamber 52, this further material is fluidized in chamber 53 by the supply of air to the plenum chamber provided by cavity 46. It is arranged that during the dipping operation the quantity of material and degree of fluidising is such that the level of material in these chambers is below the top edge of the inner chamber. At the end of a clipping operation or of a series of such operations the paddle 61 is moved as above indicated to generate a wave of fluidized material in chamber 53 to cause the material to spill over divider 51 into the chamber 52. If an excess of material has by this means been fed into the central chamber, which remains fluidized, the excess material will spill back into chamber 53, leaving the chamber 52 precisely filled at the air pressure then existing in cavity 45. The dipping operation can then by repeated as desired.

As the fluidized material is used up, it may be necessary to replenish the material in the chamber 53 from time to time, but such replenishment will be required relatively infrequently.

With reference to FIG. 5, there is shown apparatus in which components similar to those of FIG. 4 have the same reference number and suffix a. In this arrangement, there is provided above chamber 53a a plunger system comprising an air cylinder 66 operable to reciprocate a rod 67 as shown by arrow B--B and a cylindrical member 68 movable with the rod 67 and having its axis longitudinal of chamber 53a. Operation of the apparatus is similar to that described above for FIG. 4 except that at the end of a dipping operation or a series of such operations air cylinder 66 is actuated to move cylindrical member 68 into chamber 53a and thereby displace fluidized material into chamber 52a. On withdrawal of member 68, any excess material fed to chamber 52a will spill back into chamber 53a leaving the former chamber precisely filled at the air pressure then existing in cavity 450.

It will be appreciated that member 68 can be other than of cylindrical form.

It is an advantage of the arrangements described above that the dividers 21, 22, 51 and 51a are provided with surfaces which slope from the sharp edge defined at their upper edges, with the surfaces inclined. By this means it can be arranged that the material will spill easily, and without the formation of ledges of nonfluidized material, on the walls of the main chamber 26, 52 or 52a and similarly when excess material spills back from the main chamber to the supplementary chamber or chambers, after a filling operation, this material also will be less likely to form compacts of non-fluidized material on the outer walls of the dividers.

In this way it is'possible to maintain an accurate level of material in the bed for coating, so that the depth of coating on the articles is controlled principally by the mechanical dimensions of the apparatus and is not substantially affected by the variations which would normally occur in the level of the fluidized bed.

It may be convenient to arrange that the edge of the dividers are provided by replaceable inserts, rather than shaping the edges as described above.

I claim:

1. Apparatus for coating an article with a fluidized material, comprising a. a coating receptacle;

b. means for producing coating material in a fluidized condition within said coating receptacle;

0. a second receptacle;

d. means for producing coating material in a fluidized condition within said second receptacle, the level of the coating material in said coating receptacle being defined by the height of a wall separating said coating receptacle from said second receptacle;

e. means for raising the level of the coating material in the second receptacle above the height of said wall, thereby to induce the flow of material from the second receptacle to the first receptacle; and

f. means for submerging the article within the coating material contained in said coating receptacle.

2. Coating apparatus according to claim 1, wherein said level raising means comprises means for increasing the gas pressure to the second mentary receptacle.

3. Coating apparatus according to claim 1, wherein said level raising means comprises means arranged to be plumged into the coating material in the second recepticle to displace the material contained therein.

4. Coating apparatus according to claim 1, wherein said level raising means comprises means for generating a wave of additional coating material.

5. Coating apparatus according to claim 4, wherein said wave generating means comprises a pivotally mounted member. 

1. Apparatus for coating an article with a fluidized material, comprising a. a coating receptacle; b. means for producing coating material in a fluidized condition within said coating receptacle; c. a second receptacle; d. means for producing coating material in a fluidized condition within said second receptacle, the level of the coating material in said coating receptacle being defined by the height of a wall separating said coating receptacle from said second receptacle; e. means for raising the level of the coating material in the second receptacle above the height of said wall, thereby to induce the flow of material from the second receptacle to the first receptacle; and f. means for submerging the article within the coating material contained in said coating receptacle.
 2. Coating apparatus according to claim 1, wherein said level raising means comprises means for increasing the gas pressure to the second mentary receptacle.
 3. Coating apparatus according to claim 1, wherein said level raising means comprises means arranged to be plumged into the coating material in the second recepticle to displace the material contained therein.
 4. Coating apparatus according to claim 1, wherein said level raising means comprises means for generating a wave of additional coating material.
 5. Coating apparatus according to claim 4, wherein said wave generating means comprises a pivotally mounted member. 